A slightly different bowl drying question...

[David Coburn]

hello again,

Thanks for all the feedback on the small boxes and speeding up the drying process question....

I've been doing a lot of looking around on the internet and think I've come across something that I want to give a try... but.... I wanted a little feedback from you guys before I start...

I'm going to take a large wet bowl blank and go ahead and turn it wet... but I'm going to go ahead and turn it all the way to 1/4" thickness... I know it will warp and distort quite a bit... I think that this might be ok but what I don't want to happen is for it to crack or check... I was reading an article by a man named John Jordan who had this comment:

"Most woods will dry very well if turned in the 3/16 to 5/16-inch range; under most circumstances you would not need to control drying at this thickness. In the 3/8- to 1/2-inch range you may need to moderate the drying by keeping the piece in a cooler spot or a paper bag for a few days. Over 1/2 inch, you probably need to take definite steps to slow the drying for a few days or even weeks."

So what I want to do is take a 10" x 3" wet Camphor blank... turn it all the way down, let it do what its' going to do, chuck it back up so I can square up the bottom, finish sand, and apply some mineral oil and wax.... My only concern is that I don't want it to crack or check....

What are your thoughts on what I am planning?

Your expertise here has been immensely helpful over the past few weeks..

thank you,
david

[Prashun Patel]

Lots of people turn green to finish, so you're not crazy!

To improve your chances on ending with a crack-free vessel, you should create a micro-climate around the bowl that allows moisture to leave slowly. A doubled paper bag or a bucket full of dry shavings are good options. I like to remove my bowl for a couple minutes each day from the bag/bucket to allow some air exchange. This helps stymie any mold or discoloration. If you see any small checks forming, fill them with CA glue (which really won't stop all but the tiniest of fissures from opening up).

Turn to even thickness. If you are ok sanding OFF the lathe, then you can improve your chances for success by finish turning even the bottom (to remove the tenon) before the drying process.

When you sand, know that your bowl is not yet stable, which means you can create a good deal of heat that can crack the rim, so be careful and gentle.

[David Coburn]

Prashun,

thank you for the quick response... In regard to the shavings, do they need to be the ones that just came from the green bowl or can they be any shavings that you have, like from the your large parts collection on your dust collection system?

thanks,
david

[Prashun Patel]

I prefer dry shavings (I always have too many of these).
I also don't use dust from the dust collector. It's too tightly packed. The idea is to allow SOME airflow, but not too much.

[charlie knighton]

JJ signature pieces are his vases, he has to leave them 1/4 to 3/8 so he can carve on them. he also puts them in a closed wooden cabinet so he does not have any air flow for about a week til the wood has dried then carve then sand......i am sure he also does other forms......he knows a lot about wood.....awarded lifetime achievement award by AAW

[Reed Gray]

I use a recess, and it is my finished bottom. Make sure to round over the rims. I then stretch some plastic film around the outside of the rim and bowl, about 1 inch inside the bowl, and the rest on the outside. Make sure to stretch it out, which puts a little compression on the rim. I haven't tried Camphor yet, and don't know how stable it is. Some woods are very easy to dry, some are very difficult. I do start them out on the floor of the shop, away from any wind or sun. On the floor for a couple of days, and up on a wire rack for a few more days. Dry in 7 to 10 days. Sanding on the lathe is easy of you can go down to 15 to 20 rpm. If you have a 2 or 4 position spindle lock, that works too.

robo hippy

[Willem Martins]

IMHO, 1/4" is too thin if you want to do further work on it by re-chucking.

Also, 1/4" is too thick if you wish to let it dry and take its natural shape without any further lathe work.

If I plan to re-chuck, I do not go thinner than 5/8", or 10% of bowl diameter for large bowls.

If I plan to let nature take its way, without further turning, I go as thin as 1/16", use a water spray bottle to keep the piece wet while I turn and after turning put it in a double paper bag for a week, before letting it free air dry.

Here is a picture of the last one I did, with Honey Locust.

[David Coburn]

Prashun,
Ok on the dry shavings... thanks for the information.

Reed,
That is my thought as well on the bottom... Use a recess rather than a tenon... I know many warn against this, but it seems to make sense in this case. When you say "round over the rims"... Does this help with cracking at the rims or something?? what is the point of it? Also, where do you get this film? Is this just Saran wrap from Krogers or something? I do have a spindle lock so I can sand and finish as you describe..

Willem,
First, very nice bowl... I would be proud of something like that.

The rechuck is just to square off the bottom in case it did not sit flat and to provide a method for holding it so I could do some finish sanding on it and then apply the actual finish... Do these additional things fall under the "further work" comment that you had? Since this will be my 8th bowl with this lathe and 17th bowl in the past 55 years I'm not sure I'm quite up to the task of holding a 1/16th" thick wall...

thanks,
david

[George Overpeck]

It's hard to say if you would need to "control drying at this thickness" because temp/humidity/heat generated by turning will come into play, all unknown to us. If I were doing your experiment I would still control by giving the wood a little spritz of water and bagging it, but taking it out of the bag within a week. This will control for checking more than the bigger structural cracks - checking can happen within the first few hours of drying but if the very outside of the wood stays roughly equal with the interior you should be ok. You could possibly control for structural cracks by going even thinner - the wood won't have enough strength to break itself, the drying will be faster, and I would still bag it for a bit because you have some mass around the foot.

What you describe sounds like it will become is an exercise in blending the twice turned foot into the once turned form. As you sand you will have the opportunity to reflect on the best angle to have approached the foot, what the non-turning and the turning observer actually perceive or value, and the overlay of symmetry and asymmetry.

[Dennis Ford]

A 10" diameter bowl of Camphor that is 1/4" thick would dry without cracks just sitting in my shop, would probably take about a week to dry. In July or August, I would wrap it in brown paper; it would still be dry in about a week. If you leave a 1/4" tenon on a 1/4" thick piece, it is now 1/2" thick and that may be a problem (I think it would still be OK with Camphor but not nearly as confident).

[Reed Gray]

Rounding over the rim does 2 things. One is a square edge is a little razor saw, and will slice you to the bone in a micro second if you happen to brush against it. Two, by rounding over the rim, the sharp edge is far more likely to start micro cracks than a round one. My guess is that it keeps better to the 'even wall' thickness than a square edge.

Drying is a whole separate art. Each piece of wood is different, and your local environment contributes a lot to how things go. Just about perfect conditions, as confirmed by Mike Mahoney, is in his wine cellar. Cool, fairly high humidity, no sun light, no air flow. I never bother with shavings. If the shavings are wet, you can get funny colorations on the wood that won't sand out. Dry shavings, probably work well. If I was in Palm Springs, I would add moisture to the mix some way, and bagging does that. Here in western Oregon, it is generally higher humidity and cooler.

For daily use bowls, you want 1/4 inch or so. 1/16 inch is 'art'. Some of the maples and walnut seem to do fine at 3/8 inch. Much more than that, other than if you are REALLY careful, you can run into more cracks. Again, it depends a lot on local conditions.

robo hippy

[David Coburn]

Wow.... turning wet wood is very different from dry... Seems much more tame than the dry wood. I did a winged box out of dry walnut yesterday and this morning and it took me a long time... I did a 6" wet monkey pod bowl this evening and it didn't take me more than an hour... and it only took that long because I was very careful to get the walls and bottom 1/4" thick all the way around.. Since this was my first time I would cut a little bit and stop and measure, cut, stop, measure, etc.... Anyway, I got it done and put it in a paper bag and covered it up with a bunch of shavings... I'll pull it out tomorrow and let it sit for a week or two and see where it's at. I did do the recess instead of the tenon. I was concerned about the thinner area where the recess was at so I intentionally left a bit of a hump where the recess is on the inside bottom of the bowl. I'm hoping that the hump with will help with staying at 1/4" all the way around the bowl..

Anyway, I guess we'll see in a week or two just how much it will distort... I don't mind the distortion, I just don't want it to crack...

I do have a question on this... Do you guys that do this sand now or after it has dried for a while?

Oh, and I did round over the lip. Here's a picture:

wet monkey pod 1.jpg
wet monkey pod 2.jpg

david

[Breck Whitworth]

When ever I green turn to finish. I turn the walls and bottom to a consistent thickness this is more important than the actual thickness. 1/4 to 3/8 will work. Time is the enemy when green turning to finish don't take any long breaks while leaving the bowl on the lathe. I sand wet completely through the grits and get a coat of your preferred finish on it as soon as finished. I turn the outside then soak the outside with paint thinner some use naphtha. Go have a cup of coffee while it dries 20min or so, then sand the outside. The first few coarse grits discs will gum up some but I use old discs in the beginning you can blow them off and keep using them, soon the surface will be dry enough to go through the grits. Then turn the inside, when finished I flood the inside with paint thinner (cheapest I can find) then I turn up the rpms on my lathe as high as I feel safe doing and watch as the paint thinner moves through the cellular structure of the wood to the outside. Then let it dry a few minutes, then repeat the same sanding procedures for the inside. Get a coat of finish on it as soon as you finish and then add a coat every day until you are satisfied. I have NEVER had a crack just a little puckering at the end grain. These four bowls were all green turned to finish and the picture was taken 2 months after finishing them.

[Thom Sturgill]

From my experience, Camphor WILL move so be prepared for it. The shop will smell great (if you like Vicks Vaporub) and open your sinuses but be sure to clean the shavings off exposed iron or steel as the wet camphor will rust it in a heart beat. It even stained my HSS gouges.

Both John Jordan ("Life's too short to turn crappy wood" and "a cracked bowl is still a cracked bowl") and David Ellsworth talk about turning to thickness and drying by placing the piece where there is no moving air. Under Ellsworth's tutelage I turned a green rosewood spherical hollow form with the pith running side to side. It dried without cracks, but is slightly football shaped now. Turned thin, the wood can move without developing cracks.

[Doug Herzberg]

David, here's an example of what you fear. I cored this Osage Orange blank a couple months ago. I knew it wasn't dry - 18% according to my moisture meter - but I really wanted to turn something last week, so I took a chance. Wall thickness is 1/4 inch or so. Checks in the end grain showed up within a day. I bagged it and the checking stopped, or at least slowed. After a couple more days, I put on 2 coats of WOP and set it aside without the bag. Two more days and the checks are big enough to push a business card through. You can see them in the endgrain on both sides of the bowl. Osage Orange tends to check, at least the stuff I get, so I knew better.

IMG_2401.jpg